Abstract:

Taking the single season late rice varity Luoyou 2 with low cadmium absorption as the research material, under the conditions of total Cd content of 3.39 mg/kg and effective Cd content of 0.59 mg/kg in the experimental field, we set up five nitrogen fertilizer application treatments (applying pure nitrogen 0, 90, 120, 150, 180 kg/hm², denoted as N0, N1, N2, N3, N4) and three planting density treatments (240 000, 300 000, 360 000 clusters/hm², denoted as D1, D2, D3). This study aims to explore the effects of different nitrogen application rates and planting densities on rice yield, aboveground biomass accumulation, population growth rate, nitrogen fertilizer use efficiency, and Cd content in brown rice. The results showed that nitrogen application rate, planting density, and their interaction had a significant impact on rice yield. Among them, the N3D3 treatment had the highest yield, reaching 9.7 t/hm². The main reason for its high yield attributed to a higher number of effective panicles. The Cd content in brown rice of N3D1, N3D2, and N3D3 treatments was between 0.17-0.20 mg/kg, all below the safety limit standard for cadmium content in rice. Under the conditions of this experiment, the Cd content in brown rice of all nitrogen fertilizer treatments was stably below 0.20 mg/kg. With the increase of planting density, both rice yield and Cd content in brown rice showed an upward trend. When the planting density was below 378 000 clumps/hm², the Cd content in brown rice could be stably maintained below 0.20 mg/kg. In summary, when the nitrogen application rate is 150 kg/hm² and the planting density not exceeding 378 000 clusters/hm², Luoyou 2 can exert its high-yield characteristics and cadmium-low absorption characteristics, which is beneficial for achieving safe production.

Key words: rice, nitrogen application rate, planting density, yield, Cd content in brown rice, Luoyou 2

摘要：

以镉低吸收单季晚稻品种珞优2号为研究对象，在试验田块全 Cd 含量为 3.39 mg/kg、有效 Cd 含量为 0.59 mg/kg条件下，设置 5 个氮肥用量处理（分别施用纯氮0、90、120、150、180 kg/hm²，依次标记为N0、N1、N2 、N3、N4）和3个种植密度处理（分别为24、30、36万丛/hm²，依次标记为D1 、D2 、D3），旨在探讨不同施氮量和种植密度对水稻产量、地上部生物量、群体生长速率、氮肥利用率以及糙米 Cd 含量的影响。结果表明，施氮量、种植密度及其互作对水稻产量具有极显著影响，其中，以N3D3组合处理产量最高，达 9.7 t/hm²，高产主要归因于较高的有效穗数；N3D1、N3D2和N3D3处理的糙米Cd含量在0.17~0.20 mg/kg之间，均低于大米Cd含量安全限量标准。在本试验条件下，各施氮处理的糙米 Cd 含量均稳定低于 0.20 mg/kg；随着种植密度增加，水稻产量和糙米 Cd 含量均呈上升趋势；当种植密度低于 37.8 万丛/ hm² 时，糙米 Cd 含量稳定保持在0.20 mg/kg以下。综上所述，珞优2号在施氮量为 150 kg/hm²、种植密度不超过 37.8 万丛/hm²条件下，可发挥其高产特性和镉低吸收特性，从而有利于实现安全生产。

关键词: 水稻, 施氮量, 种植密度, 产量, 糙米Cd含量, 珞优2号